1. Field of the Invention
The present invention relates to an apparatus digitally detecting and displaying changes in a measurement value or more particularly a digital display apparatus of, for example, a fuel gage or voltmeter in which flickers of the displayed value are prevented.
2. Description of the Prior Art
As a display apparatus in which the flickers of the displayed value due to irregular changes (hereinafter to be called noise), other than normal changes in the measurement value, such as, for example, caused by external oscillation or variation in a load are prevented, there has been known such as disclosed in U.S. Pat. No. 4,509,044.
The one mentioned above is adapted therein such that a piece of sampling data output as a digital signal corresponding to a measurement value detected by a sensor at intervals of a predetermined period is compared with a piece of display data corresponding to a display value currently displayed on a display unit and the difference therebetween or a value corresponding to the difference is accumulated, the accumulated value is detected as to whether or not it has exceeded a predetermined range, and the display data is updated when the same has exceeded the predetermined range, and thus, irregular changes in the measurement value due to noise are absorbed and flickers of the displayed value are prevented.
However, the above mentioned prior art is of such a system that the difference between the sampling data and the display data or the values corresponding to the difference are accumulated as they are, and so, if the apparatus is provided with a slower response in order to prevent flickers due to irregular changes, or noise, other than normal changes, in the measurement value, i.e., such changes produced by small-amplitude fluctuations or narrow-width pulses as shown in FIG. 4A, there arises a problem that the response will become slower also to the real changes in the measurement value as shown in FIG. 4B. Therefore, the prior art system can be applied to a display apparatus for slowly changing measurement values, but the same, with its too slow a response, cannot be applied to a display apparatus for an abruptly changing measurement value.